Method and apparatus for the control of characteristic operating values of a power train

ABSTRACT

A first characteristic operating value, for example the amount of transmissible clutch torque, in a motor vehicle power train with an engine is controlled by using at least a second characteristic value. The second characteristic value is subject to adaptation, if necessary, during an operating phase of the motor vehicle. The method steps are::  
     starting the engine; and  
     assuring that for a predetermined first time period after starting the engine, the first characteristic operating value is controlled independently of the second characteristic value, wherein the predetermined first time period depends on at least one predetermined third characteristic operating value.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method of controlling a characteristicoperating value of a motor vehicle power train, and it also relates to acontrol device for the control of at least one characteristic operatingvalue of a motor vehicle power train.

[0002] A motor vehicle power train in the sense of the present inventionis composed in particular of the devices that are arranged in the pathalong which the power is transmitted between the drive source and thedriven wheels or driven axles of the motor vehicle, where the drivesource is in particular a combustion engine or a motor of the vehicle.In the present context, the scope of the devices that make up a powertrain is used with a broad meaning, so that control devices used tocontrol the functional parts of the power train according to the presentinvention will be considered part of the power train.

[0003] A characteristic operating value in the sense of the presentinvention is a value that can vary in magnitude during operation,particularly in the operation of a motor vehicle.

[0004] A characteristic operating value of a motor vehicle power trainin the sense of the present invention is in particular a characteristicvalue of a device that belongs to the motor vehicle power train and thatcan vary in magnitude during operation.

[0005] Methods as well as devices for controlling a characteristicoperating value of a motor vehicle power train are known among theexisting state of the art.

OBJECT OF THE INVENTION

[0006] The object of the present invention is to propose a new anddifferent method as well as a new and different control device forcontrolling a characteristic operating value of a motor vehicle powertrain.

[0007] One specific aim of the invention is to create methods as well asa control apparatus for controlling a characteristic operating value ofa motor vehicle power train that result in improved operating safety ofa motor vehicle and can be realized in a cost-effective manner and witha low level of technical complexity.

SUMMARY OF THE INVENTION

[0008] The foregoing objective is achieved in a method for controllingat least one characteristic operating value of a motor vehicle powertrain with at least one of the steps or features that are proposed inthe following description or in the claims or are illustrated in thedrawings.

[0009] A solution to meet the objective is further offered by a controldevice for controlling a characteristic operating value of a motorvehicle power train with at least one of the features that are proposedin the following description or in the claims or are illustrated in thedrawings.

[0010] A solution is offered in particular by a method of controlling afirst characteristic operating value of a motor vehicle power train,wherein the control of the first characteristic operating value undercertain conditions is performed by using at least a secondcharacteristic value, and wherein the second characteristic value isadapted if necessary during the operating phase of the motor vehiclewhen the second characteristic operating value is being used. The methodassures that for a predetermined first time period after starting theengine of a motor vehicle, the first characteristic operating value iscontrolled independently of the second characteristic operating value asthe latter may during that time period be subject to adaptation.

[0011] The operating phase of the power train or of the motor vehicle aswhole in the sense of the present invention is initiated by switchingthe ignition of the engine into the on-position, and the operating phaseis terminated by switching the ignition to the off-position.

[0012] The first characteristic operating value is in particular thetarget value for the clutch torque, or the transmissible clutch torque,or the actuating position of the clutch device.

[0013] The second characteristic value, which can in some cases be acharacteristic operating value, is in particular the contact pointposition or the friction coefficient of a clutch device.

[0014] The contact point of a clutch device in the sense of the presentinvention is in particular a position of the clutch device or of aclutch-actuating device where the clutch is at the point of becomingengaged and is able to transmit a predetermined small amount of torque.

[0015] The friction coefficient of the clutch device is in particularthe friction coefficient that exists between the friction surfaces of afriction clutch.

[0016] According to the invention, the length of the first time perioddepends on a predetermined third characteristic operating value.

[0017] The third characteristic operating value is in particular thetemperature of the engine cooling fluid or the oil temperature or theengine rpm-rate of the motor vehicle.

[0018] With preference, the first time period coincides with theso-called warm-up phase of the engine, or it coincides with an extendedwarm-up phase that includes a predetermined time delay, also referred toas offset period.

[0019] During the warm-up phase of the engine, certain characteristicoperating values are controlled differently from the subsequently usedcontrol characteristic. In particular, the warm-up controlcharacteristic takes into account that the engine usually has markedlylower temperatures after the start than during subsequent periods of thesame operating phase.

[0020] In particular, during the warm-up phase the engine rpm-rate isincreased or the fuel mixture is richer or the spark advance is setdifferently from the subsequent periods of the same operating phase. Ina richer fuel mixture, the proportion of fuel to air is larger than in aleaner mixture. The engine rpm-rate, and in particular the idling rate,is preferably increased by 250 to 450 rpm during the warm-up phase.

[0021] In the first time period of an operating phase, the secondcharacteristic value that is subject to adaptation during this timeperiod is not used for the control of the first characteristic operatingvalue, or the adaptations of the second characteristic values areblocked or not carried out. A combination of these possibilities duringthe first time period is likewise among the preferred embodiments of theinvention. In particular, the invention proposes the concept that thefirst time period includes a second time period as well as a third timeperiod that is different from the second time period. During the secondtime periods adaptations of the second characteristic values are eitheravoided or not carried out, while in the third time period, adaptationsof the second characteristic values are carried out, but the adaptedvalues are not used for controlling the first characteristic operatingvalue.

[0022] The respective lengths of the first and/or third time periods canbe different or they can remain unchanged over different operatingphases.

[0023] As a particularly preferred concept to control the firstcharacteristic operating value during the first time period, predefinedstored values are used for the second characteristic operating valueinstead of using the adapted values. The stored values can for examplebe the last adapted or last used values of the preceding operatingperiod, or they can be values that are specifically provided for useduring the first time period of different operating phases.

[0024] Preferably, the first time period is composed of the second timeperiod and the third time period that adjoins the second time period.

[0025] As a further preferred concept, the duration of the first timeperiod is different from the duration of the warm-up phase. It is inparticular proposed for the first time period to coincide with thewarm-up phase extended by a predetermined time delay.

[0026] The duration of the warm-up phase can be the same or it candiffer between different operating phases. As a preferred concept, theduration of the warm-up phase depends on a fourth characteristicoperating value which in some cases may be the third characteristicoperating value. The fourth characteristic operating value is inparticular the temperature of the cooling fluid or the oil temperatureof the motor vehicle.

[0027] The duration of the warm-up phase, or of a fourth time periodthat begins with the starting of the engine, is already defined at thetime when the engine is started or is determined after starting theengine, possibly dependent on the fourth characteristic operating value.

[0028] During the fourth time period, or during the warm-up phase and animmediately following time period, the engine or the power train iscontrolled in accordance with different characteristics including awarm-up characteristic. Preferably, the third time period extends up tothe point where a predetermined third characteristic operating valuesuch as the cooling fluid temperature has reached, exceeded or fallenbelow a predetermined threshold value for the third characteristicoperating value. With preference, the warm-up phase lasts up to thepoint where the predetermined fourth characteristic operating value,which in some cases likewise represents the cooling fluid temperature,has reached, exceeded or fallen below a predetermined threshold valuefor the fourth characteristic operating value.

[0029] Preferably, the warm-up phase extends to the point where thefourth characteristic operating value has reached a predeterminedthreshold value. The adaptation lock, i.e., the blocking of adaptationsof the second characteristic operating value or the controlling of thefirst characteristic operating value independent of secondcharacteristic values that are subject to adaptation in the sameoperating phase, is likewise tied to the condition of reaching thepredetermined threshold value. As a further preferred concept, theadaptation-locking period extends through the warm-up phase as well asan immediately following delay period. The time-delay period, likewise,is preferably tied to a predetermined threshold value of the third orfourth characteristic value, or it is a fixed time period. For example,the warm-up phase may extend to the point where the cooling fluidtemperature has reached or exceeded 40° C., and the adaptation-lockingperiod lasts until the cooling fluid temperature has reached or exceeded43° C.

[0030] It is further preferred to keep the adaptation lock in effect aslong as the engine runs at an increased rpm-rate, i.e., in accordancewith a warm-up characteristic.

[0031] The adaptation-locking time period can further be extended by apredetermined time delay period, also referred to as an offset period.

[0032] The term adaptation lock in the sense of the present inventionmeans in particular that adapted second characteristic operating valuesthat were subject to adaptation during the same operating period are notused for the control of the first characteristic operating value, orthat adaptations of the second characteristic operating values areblocked. The adaptation-locking period in the sense of the presentinvention is in particular the time period during which an adaptationlock is in effect.

[0033] The invention provides in particular a method of controlling atleast one fifth characteristic operating value of a motor vehicle powertrain, where the latter has at least one actuating device that serves toexert at least an influence over the transfer ratio of the transmissiondevice.

[0034] The aforementioned actuating device preferably includes anoperator control element such as a shift lever, and also a connectingdevice that connects the shift lever to the transmission device, so thata manipulation of the shift lever is translated by way of the connectingdevice into a corresponding actuation of the transmission.

[0035] In predetermined positions of the actuating device, the inventivemethod provides that the engagement state of the clutch device ischanged. The concept of the actuating position in the sense of thepresent invention is to be understood with a broad range of meanings.The terminology “position of the actuating device” means in particular apredetermined position of a shift lever or a predetermined variabledistance between two points of the actuating device. With preference,the connecting device includes a cable that stretches elastically inresponse to predetermined movements or forces applied to the shiftlever. Different states of stretching of this cable, i.e., changes ofthe distance between two points, are considered under the presentinvention as positions of the actuating device.

[0036] The positions of the actuating device where the engagement stateof the clutch device is changed, i.e., where the clutch is brought intoor taken out of engagement, are in the present context referred to asdisengagement thresholds.

[0037] In accordance with the invention, the disengagement thresholdsare stored in memory.

[0038] In accordance with the invention, the stored disengagementthresholds are adapted through an emergency adaptation during anoperating phase of the motor vehicle, if predetermined third conditionsare present. Such third conditions are in particular predeterminedmalfunctions in the transmission, defective components, unwanted loss ofadjustment of the transmission or the actuating device, or similarconditions that have the effect that the stored disengagement thresholdsdeviate by more than a predetermined tolerance limit from the positionsof the actuating device at which the engagement state of the clutchdevice is actually changed, i.e., where the clutch is taken out or movedinto engagement as a result of a shift lever movement.

[0039] As a further concept of the invention, at least one disengagementthreshold is adapted at the end of the operating phase of the motorvehicle if certain predetermined fourth conditions are present. Thepredetermined fourth conditions relate in particular to a situationwhere the number of gear shifts during the operating phase is largerthan a predetermined limit value. In the adaptation of the storeddisengagement thresholds, the change of the stored disengagementthresholds is limited to a first predetermined maximum value if noemergency adaptation took place during the operating phase of the motorvehicle. As a preferred concept, if the disengagement threshold is foundout of adjustment by more than the aforementioned maximum value duringthe adaptation of the disengagement threshold at the end of theoperating phase, a new disengagement threshold is stored that deviatesby the predetermined maximum value.

[0040] If an emergency adaptation was performed during the operatingphase, the change of the disengagement thresholds that is allowed duringthe adaptation that is carried out at the end of the operating phase islimited to a second maximum value. This second maximum value ispreferably a finite value that is larger than the fist maximum value.

[0041] For example, the first maximum value may be 10 increments and thesecond maximum value may be 25 increments on a linear scale of clutchtravel displacement, but these exemplary values should not be taken aslimitations of the invention.

[0042] Further proposed under the invention is in particular a method ofcontrolling at least one fifth characteristic operating value of a motorvehicle power train in which stored disengagement thresholds are adaptedthrough an emergency adaptation if predetermined third conditions arepresent. The fifth characteristic operating value is in particular theengine rpm-rate of the engine torque or the transmissible torque of theclutch device or the target value for the clutch torque or a signal thatcauses the state of engagement of the clutch to change, or the transferratio of a transmission device in a power train, or some othercharacteristic value.

[0043] According to the invention, the change of the storeddisengagement thresholds that is possible during an adaptation islimited to a predetermined first maximum value if no emergencyadaptation took place during the operating phase of the vehicle, ifpredetermined fourth conditions are present. If an emergency adaptationtook place during the operating phase of the motor vehicle, the changeis limited to a second maximum value for those disengagement thresholdsthat were subject to an emergency adaptation during the operating phase,or for a group of disengagement thresholds containing at least onethreshold that was subject to an emergency adaptation during theoperating phase. As an alternative to limiting the change to a secondmaximum value, one could also allow an unlimited change for adisengagement threshold that was subject to an adaptation during thepreceding operating phase, or for the group of disengagement thresholdscontaining a threshold that underwent an adaptation in the precedingoperating phase.

[0044] With particular preference, the limitation to the first maximumvalue is continued for adaptation changes of those disengagementthresholds that had no emergency adaptation during the precedingoperating phase or do not belong to a group containing a threshold thatwas subject to an emergency adaptation during the preceding operatingphase.

[0045] There are a variety of preferred criteria for assigning adisengagement threshold to a group. With particular preference, a groupof disengagement thresholds is assigned to those gears of thetransmission whose engagement tracks are arranged on the same side ofthe selector track in the customary shift-gate pattern of a manualstick-shift transmission. However, this particular choice of assigningdisengagement thresholds to groups should not be taken as a limitationof the invention.

[0046] The invention further proposes in particular a method ofcontrolling a fifth characteristic operating value of a motor vehiclepower train wherein during the operating phase of the motor vehicleunder predetermined third conditions at least one stored disengagementthreshold is adapted through an emergency adaptation. If none of thestored disengagement thresholds was adapted during an emergencyadaptation and if further during the operating phase at least n gearchanges were performed in the transmission, an adaptation of the storeddisengagement thresholds is performed at the end of the operating phase.The symbol n stands for a predetermined positive integer. If during theoperating phase at least one stored disengagement threshold was adaptedthrough an emergency adaptation and if at least k gear changes of thetransmission were carried out during the operating phase, an adaptationof the stored disengagement thresholds is made at the end of theoperating phase of the vehicle. The symbol k stands for a positiveinteger that is smaller than n. Thus, the number of gear changes thatleads to an adaptation of the disengagement thresholds after theoperating phase is reduced if an emergency adaptation was performedduring the operating phase. With special preference, the numbers n or krequired to cause an adaptation represent a number of gear changesinvolving one specific gear level, or all gear levels, or a specificgroup of gear levels of the transmission.

[0047] The number of gear changes required to cause an adaptation of oneor more disengagement thresholds at the end of an operating phase arethus preferably dependent on specific gears or groups of gears.

[0048] According to a preferred embodiment of the invention, n and k areselected as n=6 and k=3.

[0049] The invention provides in particular the concept that anemergency adaptation is performed during an operating phase of the motorvehicle if predetermined third conditions are present in regard to atleast one gear level or the disengagement threshold assigned to the gearlevel, in which case the emergency adaptation is performed either onlyfor the gear level where the third predetermined conditions weredetected, or for all gear levels.

[0050] The stored disengagement thresholds are used preferably forcontrolling the clutch device and/or the transmission device, inparticular in the context of a detection system that recognizes when thedriver intends to shift gears.

[0051] According to a preferred embodiment of the invention, a positionsensor is arranged at the transmission for the function of detecting amovement or a position of the transmission device, and at least oneother position sensor is arranged in the area of the shift lever or theshift gate for the purposes of detecting the movement or position of theshift lever.

[0052] The movements of the shift lever and the transmission are coupledto each other through the connecting device, but the positionalcorrelation between the shift lever and the transmission is subject toelastic deformations in the connecting device. If the sensor device onthe transmission and the sensor device on the shift lever indicatedifferent values or different travel displacements for a predeterminedshift process, it is particularly preferred to use this as an indicationthat a predetermined deformation is present in the connecting device. Ifthe predetermined deformation is larger than a predetermined thresholddeformation, this is taken as an indication that the driver intends toshift gears. This threshold deformation is in particular referred to adisengagement threshold within the context of the present invention.When the disengagement threshold is reached, this will in particularhave the effect that the clutch device is taken out of engagement. Thethreshold deformation and the arrangement for its detection are designedadvantageously in such a manner that the threshold deformation occurswhen the shift lever is moved towards the selector track or neutraltrack from a position of a fully engaged gear at the end of anengagement track.

[0053] With particular preference, the adaptation or emergencyadaptation of the stored disengagement thresholds is performedautomatically. As a preferred concept, each of the gear levels of thetransmission device has a disengagement threshold assigned to it.

[0054] The correlation between a specific gear level of the transmissiondevice and the disengagement threshold assigned to that gear level canpreferably be made automatically.

[0055] In accordance with a particularly preferred embodiment, twoposition sensors are arranged in the area of the shift lever, with afirst sensor serving to detect movements or positions of the shift leveror a connected component relative to the direction of the shift tracksand a second sensor serving to detect movements or positions relative tothe direction of the selector track.

[0056] Preferably, the connection device contains a cable that iselastically stretched as a result of certain shift processes. The cableis in particular a wire rope or a rope of some other material.

[0057] The invention provides in particular that deviations between therespective values indicated by the first and second sensor devices areused as an indication for the presence and magnitude of deformations inthe connecting device, in particular elastic deformations. Therespective values measured by the position sensors at the transmissionand the shift lever could be normalized so that the difference betweenthe values corresponds directly to the deformation. As a preferredconcept, a predetermined amount of difference or threshold differencebetween the first and second sensor signals is used to represent thedisengagement threshold. It should be noted that the respective signalvalues of the first and second position sensor devices are preferablynormalized.

[0058] As a particularly preferred concept, a third condition—i.e., acondition for adapting a stored disengagement threshold during anoperating phase of the motor vehicle—exists if an intention to shiftgears has been indicated longer than a predetermined sixth time period.The predetermined sixth time period is, e.g., 2 seconds, but thisexample should not be taken as a limitation of the invention. Acondition where an intention to shift is indicated beyond apredetermined sixth time period (permanent indication) means inparticular that a gear change and a clutch disengagement are imminent,but the gear change and clutch disengagement are not actually carriedout.

[0059] A permanent indication of an intention to shift is in particulara sign that the disengagement threshold is out of adjustment. Apermanent indication of an intention to shift can also exist if theclutch is disengaged or a gear change has taken place and an intentionto shift continues to be indicated during a predetermined sixth timeperiod.

[0060] An emergency adaptation of the disengagement thresholds ispreferable performed only for those thresholds where a predeterminedthird condition was found to be present or for a group of disengagementthresholds to which the threshold belongs that was emergency-adapted, orfor all disengagement thresholds if at least one of the disengagementthresholds was emergency-adapted.

[0061] With particular preference, at least one of the disengagementthresholds is set higher in an emergency adaptation if a permanentindication of an intention to shift was detected.

[0062] As another preferred embodiment, the invention provides a methodfor controlling a sixth characteristic operating value of a motorvehicle power train, wherein the contact point position of a clutchdevice is used under predetermined conditions for the control of thesixth characteristic operating value. The contact point position isstored and is subject to adaptation under predetermined conditions. Theinvention provides that under predetermined conditions, a creep mode ofthe clutch device is initiated. A creep mode works in particular in sucha way that the degree of engagement of the clutch device is increased inaccordance with a predetermined characteristic so that the amount oftransmissible torque increases. This operating mode is used inparticular when the vehicle is standing still or is moving at a slowspeed while the engine is running and the brake, in particular theservice brake, is substantially disengaged and the clutch device issubstantially out of engagement or transmitting a substantially smallamount of torque, and while a gear is engaged in the transmission, sothat the transmission can transmit a torque.

[0063] Moving the clutch into engagement results in an increase of theengine torque. With preference, the creep mode is performed until theengine torque has reached a predetermined level, for example 10 Nm.

[0064] Embodiments of the invention preferably include a sensor deviceto detect the engagement position of a clutch-actuating element.Dependent on the detected and indicated actuating position of theclutch-actuating element, the clutch torque or the rise in the clutchtorque is controlled. The control of the clutch torque includes inparticular the creep mode. As a preferred concept under the invention, acorrelation characteristic is provided which correlates predetermineddetected and indicated positions of the clutch-actuating element withspecific amounts of transmissible clutch torque.

[0065] According to the invention, the stored contact point is changed,in particular adapted, if the transmissible clutch torque exceeds apredetermined threshold value during a creep phase.

[0066] This feature of the invention offers in particular thepossibility to correct an out-of-adjustment condition of the contactpoint position or the stored contact point position.

[0067] A sixth characteristic operating value in the sense of thepresent invention is in particular the amount of transmissible clutchtorque or the target value for the transmissible clutch torque or theengagement position of the clutch device.

[0068] The invention proposes in particular a method of controlling atleast a sixth characteristic operating value of a motor vehicle powertrain, wherein a creep phase is initiated or performed and wherein theengine torque is monitored. The invention further provides the conceptof evaluating under predetermined conditions, whether the change of theengine torque during a predetermined time period corresponds to thechange of the targeted transmissible clutch torque during the same timeperiod.

[0069] As a preferred concept, a transmissible clutch torque iscontrolled by means of a clutch-actuating element. The clutch-actuatingelement preferably has an actuator, typically with an electric motor.With particular preference, the actuating position of theclutch-actuating element are detected or monitored. The clutch-actuatingelement preferably controls the transmissible clutch torque inaccordance with a correlation characteristic, under which an amount oftransmissible clutch torque is correlated to each clutch-actuatingposition.

[0070] The transmissible clutch torque will conform to the target inparticular if the correlation characteristic between the transmissibleclutch torque and the position of the clutch-actuating element iscorrect. If this stored correlation characteristic is incorrect, theactual transmissible clutch torque can deviate from the targetedtransmissible clutch torque. According to the invention, the correlationcharacteristic is preferably subject to adaptation.

[0071] As a preferred concept, the stored contact point or thecorrelation of the contact point with a position of the clutch-actuatingelement is changed or adapted after it was detected that the targetedchange of the transmissible clutch torque during a seventh time perioddeviates by more than a predetermined limit from the engine torquechange resulting from this control input. If not substantially all ofthe power delivered by the engine is flowing through the clutch deviceand if there are possibly other consumer devices using some of thepower, this will be taken into account in the comparison of the amountsof torque.

[0072] Preferably, the contact point is modified in the sense oflowering the contact point position. With particular preference, thecontact point is changed in steps if the changes of the engine torquedetected during the creep phase do not correspond to the targetedchanges of the transmissible clutch torque.

[0073] With particular preference, the contact point position is lowereddependent on the transmissible clutch torque, if deviations are detectedduring a predetermined time period between the changes of the enginetorque and the changes of the targeted transmissible clutch torque.

[0074] The change of the contact point is performed preferably on thebasis of a predetermined mathematical relationship.

[0075] With particular preference, the contact point position is loweredby an amount Δcp which is defined as Δcp=a×(M_(tt)−M_(limit)), wherein ais a predetermined factor, M_(tt) is the targeted transmissible clutchtorque, and M_(limit) is a predetermined limit for the targetedtransmissible clutch torque. If the targeted transmissible clutch torqueis larger than M_(limit), the contact point is lowered by Δcp. It ispossible to have a plurality of different predetermined valuesM_(limit), so that the contact point is lowered in steps.

[0076] The reference or zero point for the position of the contact pointis represented in particular by the fully engaged position of the clutchdevice.

[0077] The predetermined factor a is preferably selected as a=0.1.

[0078] In the present context, the terms “control” and “controlling” andtheir related word forms should be understood with the meanings ofregulating and controlling as defined in DIN standards.

[0079] The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain presently preferred specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Following below is a detailed explanation of the invention basedon exemplary embodiments that are illustrated in the drawings, but arenot meant as limitations on the invention, wherein

[0081]FIG. 1 represents a first example of an embodiment of the methodaccording to the invention in a schematic flow-chart format;

[0082]FIG. 2 represents a second example of an embodiment of the methodaccording to the invention in a schematic flowchart format;

[0083]FIG. 3 represents a third example of an embodiment of the methodaccording to the invention in a schematic flowchart format;

[0084]FIG. 4 represents a fourth example of an embodiment of the methodaccording to the invention in a schematic flowchart format;

[0085]FIG. 5 represents a fifth example of an embodiment of the methodaccording to the invention in a schematic flowchart format;

[0086]FIG. 6 represents a sixth example of an embodiment of the methodaccording to the invention in a schematic flowchart format; and

[0087]FIG. 7 represents a seventh example of an embodiment of the methodaccording to the invention in a schematic flowchart format.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0088]FIG. 1 illustrates the steps of a method according to theinvention in the form of a flowchart.

[0089] In step 10, the engine of the vehicle is started. In step 12, thepower train or the engine is controlled in accordance with apredetermined warm-up characteristic. In particular, the engine rpm-rateis raised by about 300 to 400 rpm during the warm-up phase.Specifically, the idling rpm-rate is raised by 300 to 400 rpm incomparison to other time periods.

[0090] In step 14, at least one predetermined first characteristicoperating value such as the transmissible clutch torque is controlled ina control mode that is independent of second characteristic values thatmay be subject to adaptation during this operating phase, such as thecontact point or the friction coefficient of the clutch.

[0091] In step 16, the cooling fluid temperature is monitored.

[0092] In step 18, the cooling fluid temperature is evaluated as towhether or not it exceeds a predetermined first limit for the coolingfluid temperature. In the affirmative case, the warm-up phase isterminated in step 20.

[0093] In the negative case of step 18, the method loops back throughsteps 12, 14, 16.

[0094] In step 22, the cooling fluid temperature is evaluated as towhether or not it exceeds a predetermined second limit. In the negativecase of step 22, the method loops back through steps 12, 14, 16. In theaffirmative case, the adaptation lock is terminated in step 24, so thatfrom this point on the first characteristic operating value iscontrolled dependent on adapted second characteristic operating values.

[0095] In step 26, the current operating phase is terminated byswitching off the ignition.

[0096]FIG. 2 represents a second example of an embodiment of theinventive method in schematic flowchart format.

[0097] The method represented schematically in FIG. 2 is distinguishedfrom the method of FIG. 1 in particular by the absence of step 22.Accordingly, if the result of step 18 is that the cooling fluidtemperature exceeds a predetermined first limit for the cooling fluidtemperature, the warm-phase is terminated and the adaptation lock islifted. In particular the latter two events occur simultaneously.

[0098] The method according to FIG. 3 is distinguished from the methodof FIG. 2 in particular by the fact that substantially at thetermination of the warm-up phase in step 20, a timer is started in step40.

[0099] The timer count is evaluated in step 42 as to whether the timeperiod from the timer start exceeds a predetermined time limit. Themethod is continued, i.e., the adaptation lock is lifted in step 24 onlyif step 42 is affirmative.

[0100] The method according to FIG. 4 is started by switching on theignition of the vehicle in step 10. At this time, a warm-up phase isstarted and initiated in step 12. In particular, during the warm-upphase the rpm-rate of the combustion engine is raised according to apredetermined warm-up characteristic in comparison to target rpm-ratesthat are set by characteristics which become operative in subsequentperiods of the same operating phase. For example, the rpm rate in anOtto-cycle engine is raised by 300 rpm, so that in particular the idlingrpm-rate is raised by 300 rpm. In a Diesel engine, the rpm-rate duringthe warm-up phase is preferably raised by about 400 rpm.

[0101] In step 14, an adaptation lock is set. The adaptation lock hasthe effect that the control of a first characteristic operating valueoccurs independently of second characteristic operating values that aresubject to adaptation during the same operating phase of the motorvehicle.

[0102] In step 50, a test is made as to whether certain criteria are metunder which the warm-up phase can be terminated. The predeterminedcriteria can be, for example, that a predetermined time period haselapsed from the time the engine was started or that a predeterminedcharacteristic operating value such as the cooling fluid temperature isbelow a predetermined threshold, or some other criterion.

[0103] In the negative case of step 50, the method loops back throughthe steps 12, 14, i.e., the warm-up phase is continued. In theaffirmative case of step 50, the warm-up phase is terminated in step 52and the engine rpm-rate is lowered from its elevated value.

[0104] In step 54, where the engine rpm-rate is no longer raised inaccordance with the warm-up characteristic, the adaptation lock islifted, so that the first characteristic operating value represented,e.g., by the transmissible clutch torque, is controlled dependent onsecond characteristic operating values which in this operating phase arebeing adapted in accordance with a predetermined characteristic. Thepredetermined characteristic can be such that adaptations take place inpredetermined time intervals or when predetermined conditions ormalfunctions are detected.

[0105] In step 56, the ignition is switched off and the operating phaseis thereby terminated.

[0106] It should be noted that the time period between the lifting ofthe adaptation lock and the switching-off of the ignition can inprinciple be of an arbitrary length and depends on the driver of thevehicle. The same is true for the methods that are illustrated in theother drawing figures.

[0107] The method shown as an example in FIG. 5 is distinguished fromthe method of FIG. 4 in particular by the fact that as soon as theengine rpm-rate is no longer at the raised level of the warm-upcharacteristic, a timer is started in step 60.

[0108] The timer count is evaluated in step 62 as to whether the timeperiod from the timer start exceeds a predetermined time limit. Themethod is continued, i.e., the adaptation lock is lifted in step 54 onlyif step 42 is affirmative. Thus, the adaptation lock is not liftedimmediately at the end of the warm-up phase as it is in the method ofFIG. 4, but with a time delay or time offset after the end of thewarm-up phase.

[0109]FIG. 6 illustrates a further example of an embodiment of a methodaccording to the invention in a schematic flowchart format.

[0110] An operating phase of the vehicle is started in step 70 byswitching on the ignition.

[0111] During the operating phase, a fifth characteristic operatingvalue of a motor vehicle can be controlled.

[0112] In step 72, movements of the transmission and movements of theshift lever are detected by at least two sensors, i.e., at least onesensor for each of the two movements. A connecting device is arrangedbetween the respective places on the transmission and the shift leverwhere the movements or positions are detected. The connecting device issubject to elastic deformations under the application of a force or inpredetermined gear-shifting situations.

[0113] Step 74 represents a test as to whether or not there is anindication that the driver intends to shift gears. An indication forsuch an intent exists in particular if the difference between therespective measured and appropriately normalized values at thetransmission and the shift lever exceeds a predetermined thresholddifference. In the negative case of step 74, the method loops back tostep 72.

[0114] In the affirmative case of step 74, a timer is started in step76. In step 78, a test is made as to whether the intention to shift isstill present.

[0115] In the affirmative case of step 78, the timer count is evaluatedin step 80 as to whether the time period from the timer start exceeds apredetermined time limit. If step 80 is negative, the method loops backto step 78.

[0116] If step 80 is positive, an emergency adaptation of the clutchdisengagement thresholds is initiated and carried out in step 80. Adisengagement threshold is in particular a predetermined differencebetween the respective normalized values measured by the positionsensors at the transmission and at the shift lever. In this particularcase, the disengagement threshold is a specific value of the differencethat is indicative of an intention to shift.

[0117] If step 78 indicates that there is no longer an intention shiftgears, the timer is set to zero in step 84.

[0118] After the emergency adaptation of the clutch disengagementthresholds in step 82 or the reset of the timer in step 84, a check ismade in step 86 as to whether a gear shift was carried out or the clutchwas taken out of engagement.

[0119] If step 86 is affirmative, a shift counter is incremented by 1 instep 88. The shift counter indicates the number of gear changes duringthe operating phase. The indication can be designed so that the sum ofall shift processes is indicated independently of which gears wereshifted, or it can be designed so that the shifts are counted separatelyaccording to gear groups that the individual gear levels are assignedto, or it can be designed to keep count separately for each of the gearsto indicate how often it was shifted into.

[0120] In the negative case of step 86, the method continues directlywith step 90.

[0121] Step 90 represents a test as to whether or not the operatingphase is to be terminated.

[0122] If step 90 is negative, the method loops back to step 72.

[0123] It should be noted that step 72 can also be performed in parallelwith the other steps of the method.

[0124] In the affirmative case of step 90, a review is made in step 92as to whether or not emergency adaptations were performed in the currentoperating phase of the motor vehicle.

[0125] If no emergency adaptation of a clutch disengagement thresholdtook place during the current operating phase, the shift counter isevaluated in step 94 as to whether the number of gear shifts performedin the current operating phase is larger than a predetermined thresholdnumber n. The threshold number n can relate to the total number of gearshifts, or to shifts in a certain group of gears, or to specific gearlevels. If the number n relates to specific groups of gears or tospecific individual gears, it is possible to set different thresholdnumbers n for the different gear groups or individual gears.

[0126] If step 92 is affirmative, a further test is made in step 96 thatis analogous to step 94 except that the threshold number in step 96 is apositive integer k that is less than n, i.e., 0<k<n.

[0127] If step 94 or 96 is negative, i.e., if the number of shifts inthe operating phase was smaller than the applicable threshold value n ork, the ignition is switched off in step 104 and the operating phase isthereby terminated.

[0128] If step 94 is affirmative, the method proceeds to step 98 where alimit is set for a maximum amount by which the clutch disengagementthreshold is allowed to be changed in the subsequent adaptation thattakes place in step 102.

[0129] After the adaptation has been carried out in step 102, theignition is switched off and the operating phase is thereby terminated.

[0130] In the affirmative case of step 96, i.e., if the number of gearshifts is at or above the limit for performing an emergency adaptation,the method proceeds to step 100 where a limit is set for a maximumamount by which the clutch disengagement threshold is allowed to bechanged in the subsequent adaptation that takes place in step 102. Thelimit set in step 100 is larger than the limit set in step 98.

[0131] The limits set in step 98 as well as in step 100 are of finitemagnitude.

[0132]FIG. 7 illustrates a further example of a method according to theinvention.

[0133] In step 120, a creep phase is initiated if predeterminedconditions are present that are indicative of the need for a creepphase. The predetermined conditions are in particular:

[0134] the vehicle speed is smaller than a predetermined vehicle speed,or the vehicle is standing still,

[0135] a gear is engaged,

[0136] the brake, in particular the service brake or the parking brake,is not actuated,

[0137] the accelerator pedal is not actuated,

[0138] the engaged gear is a start-up gear such as first, second orreverse gear.

[0139] In step 122, a timer is started.

[0140] In step 124, a creep phase is performed, meaning that a clutchtorque or a control target for the clutch torque is built up in aramp-shaped time profile according to a predetermined creepcharacteristic, which causes an increasing degree of engagement of theclutch device.

[0141] During step 124, the clutch torque is monitored in step 126,preferably by monitoring the amount of displacement of a clutchactuating element or other element in the actuating chain.

[0142] Step 128 represents a test as to whether or not the clutch torqueis larger than a predetermined limit that was set for the clutch torque.

[0143] In the affirmative case of step 128, the conclusion is made instep 130 that the contact point of the clutch is out of adjustment, andthe contact point is adjusted in step 130. The procedure for this is inparticular that the contact point is set lower and that instead of thepreviously stored contact point, the adjusted (i.e., lowered) contactpoint is stored. The lowering of the contact point position can beperformed in steps of predetermined equal amounts or according to aformula which may be of a linear or of some other character, or theadjustment may be performed in some other way.

[0144] For example, a differential amount Δcp may be subtracted from thestored contact point position according to the formulaΔcp=a×(M_(tt)−M_(limit)), wherein the factor a is preferably set at 0.1mm per Nm. For example, if M_(limit)=25 Nm and M_(tt)>25 Nm, thecorrection is calculated as Δcp=a×(M_(tt)−25) [mm].

[0145] In the negative case of step 128, the method proceeds to step132, where the timer is evaluated as to whether or not the indicatedtime period is longer than a predetermined time limit.

[0146] In the affirmative case of step 132, the method proceeds to step130 for an adjustment of the contact point position.

[0147] In the negative case of step 132, the method proceeds to step 134for a test as to whether or not a condition is met for terminating thecreep phase. An appropriate condition for this is in particular that,since the initiation of the creep phase, the engine torque has increasedby a predetermined amount such as, e.g., 10 Nm.

[0148] In the negative case of step 134, the method loops back tocontinue at step 124.

[0149] After the contact point position has been changed in step 130,the method continues at step 134.

[0150] In the affirmative case of step 134, the creep phase isterminated in step 136 and the power train—or more specifically, thecharacteristic operating values including the transmissible clutchtorque—are subsequently controlled under another characteristic that isdifferent from a creep characteristic.

[0151] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic and specific aspects of theaforedescribed contribution to the art and, therefore, such adaptationsshould and are intended to be comprehended within the meaning and rangeof equivalence of the appended claims.

What is claimed is:
 1. A method of controlling a first characteristic operating value of a motor vehicle power train with an engine, wherein the control of the first characteristic operating value under predetermined conditions is performed by using at least a second characteristic value, and wherein the second characteristic value is subject to adaptation if necessary during an operating phase of the motor vehicle, said method comprising the steps of: starting the engine; and assuring that for a predetermined first time period after starting the engine, the first characteristic operating value is controlled independently of the second characteristic value, wherein said predetermined first time period depends on at least one predetermined third characteristic operating value.
 2. The method of claim 1, wherein during the predetermined first time period, the adaptation of the at least one second characteristic value is blocked.
 3. The method of claim 1 wherein, if the second characteristic value was adapted during the operating phase, the second characteristic value is not used for the control the first characteristic operating value during the first time period.
 4. The method of claim 1, wherein the first time period comprises a second time period and a third time period, the third time period being different from the second time period, wherein the adaptation of the at least one second characteristic value is blocked during the second time period, and wherein if the at least one second characteristic value was adapted during the operating phase, it is not used for controlling the first characteristic operating value during the third time period.
 5. The method of claim 4, wherein the first and third time periods are of different length during different operating phases.
 6. The method of claim of claim 4, wherein the first and third time periods last until the at least one third characteristic operating value has reached or passed through a predetermined threshold for the third characteristic operating value.
 7. The method of claim 1, wherein the at least one second characteristic value belongs to the group of characteristic values consisting of a characteristic value of a clutch device, a characteristic value of a transmission device, and further characteristic values of a motor vehicle.
 8. The method of claim 7, wherein the at least one second characteristic value comprises a contact point position of one of a clutch actuator device and the clutch device, wherein at said contact point position the clutch device has a degree of engagement at which a torque begins to be transmitted through the clutch device.
 9. The method of claim 7, wherein the at least one second characteristic value comprises a friction coefficient of the clutch device.
 10. The method of claim 1, comprising the further steps of: controlling the engine in accordance with at least a first operating characteristic during a predetermined fourth time period immediately following the starting of the engine; and controlling the engine in accordance with at least a second operating characteristic after the predetermined fourth time period has elapsed.
 11. The method of claim 10, wherein a duration for the fourth time period is set when the engine is started.
 12. The method of claim 10, wherein the fourth time period is of equal length in different operating phases.
 13. The method of claim 10, wherein the fourth time period is of different length in different operating phases.
 14. The method of claim 10, wherein the fourth time period depends on at least one fourth characteristic operating value.
 15. The method of claim 10, wherein the fourth time period lasts until a predetermined fourth characteristic operating value has reached or passed through a predetermined threshold for the fourth characteristic operating value.
 16. The method of claim 10, wherein the third and fourth characteristic operating values belong to the group that consists of a cooling fluid temperature and an oil temperature and an rpm-rate of the motor vehicle.
 17. The method of claim 10, wherein the first time period has a length corresponding to the sum of the fourth time period and an offset time period that immediately follows the fourth time period.
 18. The method of claim 17, wherein the offset time period has a predetermined constant length.
 19. The method of claim 17, wherein said predetermined constant length depends on the third and fourth characteristic operating values.
 20. The method of claim 10, wherein the adaptation of the second characteristic value is blocked during the fourth time period.
 21. The method according to claim 10, wherein the fourth time period equals the first time period.
 22. The method of claim 1, wherein the motor vehicle power train comprises an automated clutch device.
 23. A method of controlling at least a fifth characteristic operating value of a motor vehicle power train with a clutch device, a transmission device, and an actuating device by means of which a control of a transmission ratio of the transmission device can at least be influenced, wherein the actuating device comprises clutch-disengagement thresholds at which a state of engagement of the clutch device is changed; and wherein the clutch-disengagement thresholds are stored in memory, said method comprising the steps of: performing an emergency adaptation of at least one of the stored clutch-disengagement thresholds during an operating phase of the motor vehicle, if predetermined third conditions are present; and performing a non-emergency adaptation of at least one of the stored clutch-disengagement thresholds at the end of said operating phase if predetermined fourth conditions are present.
 24. The method of claim 23, wherein said non-emergency adaptation is limited to a first maximum value if no emergency adaptation of a stored clutch-disengagement threshold occurred during the operating phase, and wherein said non-emergency adaptation is limited to a second maximum value if an emergency adaptation of a stored clutch-disengagement threshold occurred during the operating phase.
 25. The method of claim 23, wherein said non-emergency adaptation is limited to a first maximum value for those of the clutch-disengagement thresholds that belong to a group of clutch-disengagement thresholds in which no emergency adaptation occurred during the operating phase, and wherein said non-emergency adaptation is limited to a second maximum value or not subject to any limit for those of the clutch-disengagement thresholds that belong to a group of clutch-disengagement thresholds in which an emergency adaptation occurred during the operating phase.
 26. The method of claim 23, wherein the second maximum value is different from the first maximum value.
 27. The method of claim 26, wherein the second maximum value is larger than the first maximum value.
 28. The method of claim 23, wherein said non-emergency adaptation is performed under one of the conditions that: no emergency adaptation of a stored clutch-disengagement thresholds occurred during the operating phase and at least a number n of gear-shifts were performed in the transmission device during the operating phase, n being a positive integer; and at least one emergency adaptation occurred during the operating phase and at least a number k of gear-shifts were performed in the transmission device during the operating phase, k being a positive integer smaller than n.
 29. The method of claim 28, wherein n and k represent numbers of gear-shifts that were performed during the operating phase, wherein the numbers n and k are counted for one of the following: for one individual gear level of the transmission device, for each individual gear level of the transmission, for a predetermined group of gear levels of the transmission, or for all gear levels of the transmission.
 30. The method of claim 23, wherein said predetermined third conditions relate to at least one clutch-disengagement threshold that is assigned to a predetermined gear level of the transmission device, and wherein the emergency adaptation is performed in one of three ways, namely: a first way consisting of adapting only the clutch-disengagement threshold related to the predetermined third conditions, a second way consisting of adapting all clutch-disengagement thresholds of a predetermined group containing the clutch-disengagement threshold related to the predetermined third conditions, and a third way consisting of adapting all of the clutch-disengagement thresholds.
 31. The method of claim 23, wherein the at least one stored clutch-disengagement threshold is used to control at least one of the clutch device and the transmission device.
 32. The method of claim 23, wherein at least one of the emergency adaptation and the non-emergency adaptation is performed automatically.
 33. The method of claim 23, wherein the transmission device has at least two gear levels and a clutch-disengagement threshold is correlated with each of the at least two gear levels.
 34. The method of claim 33, wherein the correlation between clutch-disengagement thresholds and gear levels is made automatically.
 35. The method of claim 23, wherein the actuating device comprises an operator control element that is connected to the transmission device through a connecting element.
 36. The method of claim 35, wherein the connecting element comprises a mechanical cable connection.
 37. The method of claim 35, wherein the transmission device comprises at least one first position sensor device to detect predetermined first positions of the transmission device and at least one second position sensor device to detect predetermined second positions of the operator control element.
 38. The method of claim 37, wherein under predetermined conditions a deviation between a predetermined first position and a predetermined second position is indicative of an elastic deformation of the connecting element.
 39. The method of claim 38, comprising the further step of detecting when an operator of the motor vehicle intends to shift gears in the transmission device, wherein said detection is based on recognizing when a force is applied to the operator control element towards a shift position where at least one of a gear shift and a clutch disengagement will occur, and wherein said detection occurs before said shift position is reached.
 40. The method of claim 39, wherein said detection is based on evaluating at least one of said first and second positions.
 41. The method of claim 39, wherein said detection is based on evaluating said deviation, and wherein said intention to shift gears is found to be present if, over a time interval that is longer than a predetermined fifth time period, the deviation is larger than a predetermined limit value for said deviation.
 42. The method of claim 37, wherein a predetermined magnitude of a deviation between a predetermined first position and a predetermined second position is indicative of at least one of the clutch-disengagement thresholds.
 43. The method of claim 39, wherein the predetermined third conditions are that an intent to shift was detected to be present during a time interval exceeding a predetermined sixth time period.
 44. The method of claim 43, wherein the predetermined sixth time period is 2 seconds.
 45. The method of claim 30, wherein said emergency adaptation is performed in the first way.
 46. The method of claim 30, wherein said emergency adaptation is performed in the second way.
 47. The method of claim 30, wherein said emergency adaptation is performed in the third way.
 48. The method of claim 35, wherein the at least one clutch-disengagement threshold is used under predetermined conditions, if a movement of the operator control element indicates that in order to shift out of a currently engaged gear level, the clutch device it to be moved at least partially out of engagement.
 49. A method of controlling at least one sixth characteristic operating value of a power train in a motor vehicle comprising an engine producing an engine torque, a clutch device transmitting a clutch torque, a brake device, a transmission device with at least one gear level, and a gas pedal, wherein under certain predetermined conditions, said controlling is performed by using a contact point position of the clutch device, said contact point position being stored in memory and being subject to adaptation under predetermined conditions, said contact point position representing a state of the clutch device or of a clutch-actuating device where the clutch device is at the point of becoming engaged and is able to transmit a predetermined small amount of torque, the method comprising: the step of initiating a creep phase of the clutch device, wherein during said creep phase the clutch device is moved into an increasing degree of engagement until an increase of the engine torque caused by said increasing engagement has reached a predetermined engine torque value; the brake is in a disengaged state and said at least one gear level is in an engaged state; the gas pedal is not being actuated; an increase in the clutch torque or in a control target value for the clutch torque is controlled as a function of a position of a clutch-actuating element as detected by a position sensor; and a correlation characteristic correlates predetermined positions of the clutch-actuating element to predetermined amounts of transmissible torque of the clutch device; the further step of changing a stored value for the contact point position, if one of the clutch torque and the control target for the clutch torque exceeds a predetermined limit.
 50. A method of controlling at least one sixth characteristic operating value of a power train in a motor vehicle comprising an engine producing an engine torque, a clutch device transmitting a clutch torque, a brake device, a transmission device with at least one gear level, and a gas pedal, wherein under certain predetermined conditions, said controlling is performed by using a contact point position of the clutch device, said contact point position being stored in memory and being subject to adaptation under predetermined conditions, said contact point position representing a state of the clutch device or of a clutch-actuating device where the clutch device is at the point of becoming engaged and is able to transmit a predetermined small amount of torque, the method comprising the steps of: a) initiating a creep phase of the clutch device, wherein during said creep phase the clutch device is moved into an increasing degree of engagement according to a predetermined characteristic; the brake is in a disengaged state and said at least one gear level is in an engaged state; the gas pedal is not being actuated; an increase in the clutch torque or in a control target value for the clutch torque is controlled as a function of a position of a clutch-actuating element as detected by a position sensor; and a correlation characteristic correlates predetermined positions of the clutch-actuating element to predetermined amounts of transmissible torque of the clutch device; b) monitoring the engine torque; and c) evaluating whether a controlled change in the transmissible torque of the clutch device conforms to a change in the engine torque that was caused by said controlled change.
 51. The method of claim 50, comprising the further steps of: d) changing or adapting the contact point position, and e) assigning the contact point position to a position of the clutch-actuating element, if the controlled change in the transmissible torque of the clutch device during a seventh time period was found to deviate by more than a predetermined limit from the change in the engine torque that was caused by said controlled change.
 52. The method of claim 49, wherein the sixth characteristic operating value represents a target value for the transmissible torque of the clutch device.
 53. The method of claim 49, wherein the contact point position is changed by lowering the contact point position, and wherein the contact point position is related to the distance between the position of beginning engagement and the position of full engagement of the clutch device.
 54. The method of claim 50, wherein the contact point position is changed by lowering the contact point position, and wherein the contact point position is related to the distance between the position of beginning engagement and the position of full engagement of the clutch device.
 55. The method of claim 53, wherein the lowering of the contact point position is performed in steps.
 56. The method of claim 54, wherein the lowering of the contact point position is performed in steps.
 57. The method of claim 53, wherein the lowering of the contact point position is performed dependent on the transmissible torque of the clutch device.
 58. The method of claim 54, wherein the lowering of the contact point position is performed dependent on the transmissible torque of the clutch device.
 59. The method of claim 53, wherein the lowering of the contact point position is performed according to a predetermined mathematical relationship.
 60. The method of claim 54, wherein the lowering of the contact point position is performed according to a predetermined mathematical relationship.
 61. The method of claim 53, wherein the contact point position is lowered by an amount Δ_(CP) according to the formula Δ_(cp)=a×(M_(tt)−M_(limit)), wherein a represents a predetermined factor, M_(tt) represents the targeted amount of transmissible clutch torque, and M_(limit) represents a predetermined threshold for the targeted amount of transmissible clutch torque, so that when M_(limit) is exceeded, the lowering of the contact point position is performed according to said formula.
 62. The method of claim 54, wherein the contact point position is lowered by an amount Δ_(CP) according to the formula Δ_(cp)=a×(M_(tt)−M_(limit)), wherein a represents a predetermined factor, M_(tt) represents the targeted amount of transmissible clutch torque, and M_(limit) represents a predetermined threshold for the targeted amount of transmissible clutch torque, so that when M_(limit) is exceeded, the lowering of the contact point position is performed according to said formula.
 63. The method claim 61, wherein a represents 0.1 mm per Nm.
 64. The method claim 62, wherein a represents 0.1 mm per Nm.
 65. A control apparatus for controlling at least one characteristic operating value of a motor vehicle power train, wherein the control apparatus performs the method according to claim 1 in an at least partially automated way.
 66. A control apparatus for controlling at least one characteristic operating value of a motor vehicle power train, wherein the control apparatus performs the method according to claim 23 in an at least partially automated way.
 67. A control apparatus for controlling at least one characteristic operating value of a motor vehicle power train, wherein the control apparatus performs the method according to claim 49 in an at least partially automated way.
 68. A control apparatus for controlling at least one characteristic operating value of a motor vehicle power train, wherein the control apparatus performs the method according to claim 50 in an at least partially automated way. 